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rec.radio.amateur.boatanchors

good luck



"SpamLover" wrote in message
m...
Goal:
* Minimum fuss 3-30MHz operation, mostly on 5-15MHz.
* Will use step-dowm RF transformer between antenna and low impedance
coax
* May use autotuner on TX
* Like the wirecage antennas still today seen on many a military
vessel.

Available on roof:
- 25ft steel structure (like piramid base for power line)
- about 100 feet space in one direction
-...to abandoned flue chimney, 100ft away and 10 feet lower than base
of steel structure
- roof covered with alu plates on tar (could be all arc welded
together, perhaps.

THIS LOOKS PRETTY MUCH LIKE A SHIP TO ME cept its' 120ft aboveground.

I want to build a wire cage monopole
- sloping down from steel tower
- using tower as counterpoise
- feedpoint at top of sloper, via stepdown rf transfomrer, grounded to
tower
- coax cable lead, with rf choke coils and surge suppressors.

Questions:
- what kind of cage antenna?
- how many wires?
- what spreaders, how large?
- ideal wire?

Current plan config:
- length 14 m = 2 x 4m straight sections, + 2 x 3m truncated cubes
- spreaders at 3-7-11 m
- 140 cm dia. spreaders, each made with two waterproofed bamboo
triangles in "star of David" configuration; wire kept parallel at 70cm
distance from each orther.
- material: .8mm copperclad, abt. 90 m (270 ft) total.

Any hints, like more/fewer parallel wires, broader / smaller
spreaders, different materials, dirrerent antenna wire, RF
downtransformer, whatever?

Filippo

Dear W4JLE

I think you should be aware that, as perceived at the receiver end, the
characteristics of the feedline, its length and SWR, and tuner can have at
least as great an effect on operating bandwidth as the antenna constuction
itself. Antenna height above ground can seriously affect bandwidth.
Lowering height can increase bandwidth more than changing from from a thin
wire to big fat cage.

There's far too much attention paid to the subject of wire diameter by the
gurus who have heard a rumour that wire diameter increases bandwidth and
can't resist repeating the story on every possible occasion. I produced the
program to put the matter into quantitative perspective.

As for a fat antenna's remarkable ability to distinguish favourably between
signals and noise I can suggest only that your A-B tests were not quite what
you thought they were. Displacement, orientation, noise in a null,
different receiver?

With MY neighbours the only warm fuzzy feelings have to be alcohol-assisted.
---
Reg
====================================

"w4jle" W4JLE(remove this to wrote in message
...
Reg, in A/B tests with a standard dipole, the cage was "quieter". That is,
I
am able to hear weaker signals with less noise. Anecdotal at best, but
keeps
me using one.

I am under 2:1 from 3575 to 3925 with no tuner. I suspect that if I were
using copper Vs the fence wire the Q would be higher and the results more
in
agreement with your cage program.

Besides it gives me a warm fuzzy feeling and impresses the neighbors.


"Reg Edwards" wrote in message
...
The only difference in performance between a cage antenna and an
ordinary
thin-wire dipole is a modest increase in bandwidth. There is no
increase
in
radiating/receiving efficience.

The increase in bandwidth is much less than is popularly supposed and
may
not be considered worth the extra construction costs and inconvenience.

To predict resonant frequency, bandwidth and a few other characteristics
from overall length, number of cage wires from 1 to N, and wire
diameter,
download program DIPCAGE from website below.

Download DIPCAGE in a few seconds, no unzipping inconvenience, run
immediately.
----
=======================
Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
=======================

SpamLover,

http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm

http://www2.arrl.org/news/stories/2001/05/03/2/

http://www.pust-norden.de/oloog/oloog-2_gr.jpg

http://www.qsl.net/wa2tvs/antennas/archive17.htm

http://www.antenna.be/tel-ave0640.html


iane ~ RHF
..
..
= = = (SpamLover)
= = = wrote in message om...
Goal:
* Minimum fuss 3-30MHz operation, mostly on 5-15MHz.
* Will use step-dowm RF transformer between antenna and low impedance
coax
* May use autotuner on TX
* Like the wirecage antennas still today seen on many a military
vessel.

Available on roof:
- 25ft steel structure (like piramid base for power line)
- about 100 feet space in one direction
-...to abandoned flue chimney, 100ft away and 10 feet lower than base
of steel structure
- roof covered with alu plates on tar (could be all arc welded
together, perhaps.

THIS LOOKS PRETTY MUCH LIKE A SHIP TO ME cept its' 120ft aboveground.

I want to build a wire cage monopole
- sloping down from steel tower
- using tower as counterpoise
- feedpoint at top of sloper, via stepdown rf transfomrer, grounded to
tower
- coax cable lead, with rf choke coils and surge suppressors.

Questions:
- what kind of cage antenna?
- how many wires?
- what spreaders, how large?
- ideal wire?

Current plan config:
- length 14 m = 2 x 4m straight sections, + 2 x 3m truncated cubes
- spreaders at 3-7-11 m
- 140 cm dia. spreaders, each made with two waterproofed bamboo
triangles in "star of David" configuration; wire kept parallel at 70cm
distance from each orther.
- material: .8mm copperclad, abt. 90 m (270 ft) total.

Any hints, like more/fewer parallel wires, broader / smaller
spreaders, different materials, dirrerent antenna wire, RF
downtransformer, whatever?

Filippo

What kind of bandwidth do you get with that?

Bob AD3K

w4jle wrote:
Might I suggest electric fence wire, a 1/4 mile spool is under $8.00. 19 AWG
and designed for outdoor use.

I have used cage dipoles for years and it has worked well for me. I normally
use 6 wires and slices of 12" diameter plastic sewer pipe cut to 1/4 inch
thickness and 6 holes drilled every 60 degrees(slightly larger than your
wire). on 80 meters I use 4 rings per side equally spaced. the rings are
held in place by winding a short piece of wire around the plastic and
twisting it on each side of the ring to the antenna element.

G4FGQ:

The only difference in performance between a cage antenna and an ordinary
thin-wire dipole is a modest increase in bandwidth. There is no increase in
radiating/receiving efficience.


Measurements by K8CFU found "surprising" increase in signal strenght from
folded dipole/cage vs. straight radiator.

- another subject for unbelievers, measure it and see what it really is.

Yuri, www.K3BU.us

Thus the reason they make chocolate and vanilla, we all get a choice.

I choose the cage, don't confuse me with the facts.


"Reg Edwards" wrote in message
...
Dear W4JLE

I think you should be aware that, as perceived at the receiver end, the
characteristics of the feedline, its length and SWR, and tuner can have at
least as great an effect on operating bandwidth as the antenna constuction
itself. Antenna height above ground can seriously affect bandwidth.
Lowering height can increase bandwidth more than changing from from a thin
wire to big fat cage.

"Yuri Blanarovich" wrote
Reg Edwards wrote
The only difference in performance between a cage antenna and an ordinary
thin-wire dipole is a modest increase in bandwidth. There is no increase
in
radiating/receiving efficience.


Measurements by K8CFU found "surprising" increase in signal strenght from
folded dipole/cage vs. straight radiator.

- another subject for unbelievers, measure it and see what it really is.

===================================

Emotional systems of measurement are becoming fashionable on this newsgroup.

How many Centibels are there in one Surprise?

How many Surprises are there in one Heart Attack?

Frederick Emmons is turning over.

Thank you all again for the deluge of tips & links!
This is getting seriously fun!

Quick update on my trials with copperclad (maybe just copperflashed)
metal-inert-gas continuous welding steelwi

- This stuff solders like heaven! Steel disperses heat less than
copper, and capillarity is amazing. Hot solder joints catch deep
between twisted wires.

- Steel is quite springy and retains shape. My spool is small (~5"
dia.) but if I release the wire it falls into 15" loops.

- I made a 20' dia. loop with 3+ rounds of this wire, and soldered it
at 6 spots all round. Very light and elastic.

You know where I'm heading. I would like to try a lightweight soldered
all-steel cage, and rustproof it with one of those steel-blackening
nitric acid paints.

As a trial, I'd do a short cage with two 20" rings, maybe 2' between
them, and 3' end cones, paint it all, and hang it out in the elements,
weight-loaded.

The INEVITABLE QUESTION
=== Do cage spreaders HAVE to be insulating? ===

Uneducated guess: as VHF/UHF discones are made out of either radials
or sheet metal, I'd say that shorting spacers should be OK.

Reg, G4FGQ shines with:

Emotional systems of measurement are becoming fashionable on this newsgroup.
How many Centibels are there in one Surprise?
How many Surprises are there in one Heart Attack?
Frederick Emmons is turning over.


Snotty remarks are even more fashionable on this and other newsgroups.

Why would you say that? Do you know who K8CFU is? Do you know what kind of work
has he and associates done? Did you read his articles about some findings? Did
you talked to him about some stuff that was not published?

Do you know EVERYTHING and have programs to calculate it RIGHT?
Are you another W8JI who "knows" everything and ridicules others?
Now measurements by someone else are wrong, but speculations based on limited
knowledge are the "law"?
So did you unemotionaly measure any of that stuff yet, or you "know" it?

I gladly discuss and argue about technical or other stuff, but I don't take a
crap and I bite back. Some would have figured that by now and adjusted their
way of communicating.

You seem to jump up without doing the homework and then missing the point and
may end up looking foolish.


Yuri, K3BU/m

The INEVITABLE QUESTION
=== Do cage spreaders HAVE to be insulating? ===

YES for sure, for sure. The cage should be really folded dipole, one "wire"
going up (support, and grounded at the bottom) the other wire on the outside
(cage) coming down and fed against the ground or radials. Unless you just want
to make it fat radiator, then it doesn't matter.

When working with welding wire, try not to scratch it. It has very thin copper
layer, easy to scratch and then start corrosion and destruction of the wire.
You might want to put some coat of paint over it if you intend to keep it for
long. Epoxy paints or marine varnish are the best.

Yuri, K3BU